Centrifugal fan wheel



Dec. 19, 1961 sMn-H ETAL 3,013,714

CENTRIFUGAL FAN WHEEL Filed Sept. 28, 1960 INVENTORS RALPH B. SMITH CHARLES G. TOLSON ATTORNEY United States l near Qfidce 3,613,714 Patented Dec. 19, 1961 This invention relates to improvements in centrifugal fan wheel construction.

Some difficulty has been experienced with centrifugal fan Wheels which have been damaged or destroyed dur ing operation with excessive wobble and imbalance resulting from an inclination of the plane in which the fan wheel backplate lies relative to tr plane perpendicular to the axis of the driving shaft. One factor contributing to such a tilted fan wheel has been found to reside in a warped or distorted bacltplate resulting from uneven expansion and contraction thereof caused by'heating and cooling of the backplate during and after welding of the fan blade ends to the outer annular portion of the backplate. A warped backplate may cause the average plane in which the backplate lies to be inclined to some degree from. a plane perpendicular to the axis of the driving shaft of the fan wheel.

Objects of the present invention are to provide a centrifugal fan wheel construction which: substantially avoids the problem of warping of the backplate member from the welding operation; has parts thereof arranged in a manner which facilitates the fabrication of parts and assembly thereof from a manufacturing standpoint; and results in a structurally and operationally superior wheel.

In accordance with the invention the backpl-ate, or what is sometimes called the central disc in connection with double Width fan wheels, is formed of: an annular member having an outer peripheral or annular portion to which the ends of circumferentially-arranged, axiallyextending fan blades are attached, and an inner peripheral or annular portion of a segmented configuration; and a hub carrying disc having an outer diameter sufficient to lap the inner annular portion of the annular member but not the outer annular portion to which the blade ends are secured. The blade ends, which preferably have tabs projecting through corresponding slots in the outer annular portion of the annular member, are held in secured relation thereto by applying one or more weld beads to the exterior face of the outer annular portion and over the tab end edges which are flush with the face. While the heat from welding conducted to the inner annular portion causes some expansion of the individual segments, they are free to expand, and subsequently contract upon cooling, without substantial warping or buckling out of their initial plane due to the spaces between the segments. Hence when the annular member is fastened to the hub carrying disc, the average plane of the backplate assembly lies in a plane perpendicular to the driving shaft axis rather than being inclined therefrom. Further, the annular member is fastened to the disc by fastening members, such as bolts, which pass through the central portion of the individual segments of the inner peripheral portion and thus flatten the segments against the disc and reduce, in an average fashion, any warping experienced by individual segments. Since the hub carrying disc preferably does not extend radially outwardly to lap the outer annular portion of the annular member, it also does not lap or engage the weld beads thereon, and imperfections in the nature of non-uniformity of the mass of Weld material at different locations on the surface does not result in inclining the fan wheel axis relative to the driving shaft axis.

The invention is particularly applicable in connection where both wheels have the weld bead ridges facing each other when assembled in mirror relation. In this case the central disc of reduced outer diameter, relative to the outer diameter of the annular members, serves to space the annular members sufliciently in an axial direction to avoid contact between the weld beads so that non-uniformity of the weld beads in such an assembly does notcause the noted misalignment.

The invention will be explained in some detail in connection with the accompanying drawing illustrating a centrifugal fan wheel incorporating the principles of the invention in one embodiment by way of example, and wherein:

FIGURE 1 is a view of the fan wheel with the left end portion in elevation, and with the remainder of the view being a section taken along line 11 of FIGURE 2;

FIGURE 2 is an end view of the fan Wheel;

FIGURE 3 is a view in section of the fan wheel, this I view being taken along a line corresponding to the line 3--3 of FIGURE 1, and with part of one annular member being broken;

FIGURE 4 is an enlarged exploded view of fragments of an end ring and a blade end to illustrate their preferred construction.

The illustrated embodiment of the invention is a double inlet, double width centrifugal fan wheel of the type wherein air is drawn axially into the wheel from both open ends and is then impelled in a radial direction to the outlet of a scroll (not shown). Since the left and right hand wheels of FIGURE 1 are of generally the same construction but assembled in mirror relation to each other, the description will deal, for the most part, with only one of the two wheels.

Referring to FIGURES 13, the left wheel 2 includes a number of separate, shaped blades 4 arranged circumferentially about the central axis of the Wheel with the eft ends of the blades secured to the flat endring or rim 6 and the right ends of the blades secured to an opposite annularly-shaped member 8. The end ring 6 has unbroken inner and outer peripheral edges (FIGURE 2) while the annular member 3 has an outer peripheral edge which is unbroken but an inner peripheral edge which is broken by slots or notches lii. The central opening of member 8 is also of a considerably smaller diameter than the central opening of the end ring 6. The inner annular portion of the member 8 is identified in FIGURES 2 and 3 by the numeral 12 while the outer annular portion, which serves the same function as the outer end ring 6 insofar as it receives the ends of the blade 4, is identified by the numeral 14.

The parts of the left wheel 2 described thus far form, when assembled, a circular cage-shaped rotor having a larger central opening on the left end than on the right end. The right wheel 16 would form a similar structure with its larger central opening being to the right of FIGURE 1 and its smaller central opening being in the center part of FIGURE 1, the right wheel blades being identified by the numeral 13, the right end ring or rim being designated 20 and the inner annular member being designated 22.

The presently preferred mode of securing the blade ends to the end rings to initially form separate wheels is representatively shown in FIGURE 4 which, for example purposes, illustrates the left end of a blade 4 and the left end ring'6 in disassembled relation, both ends of the blades of both wheels being secured to the respective end ring members in the same fashion. Each end of each with double inlet, double width centrifugal fan Wheels blade 4 and 18 is provided with a tab '24 which projects longitudinally past the blade end or shoulder 26. While the blade as a whole is normally of a simple arcuate cross section, the projecting tab has flat opposite faces sothat the slot 28 punched out of the end ring 6, and into which the tab is inserted, may be of a rectangular configuration. Projection of the tab 24 past the shoulders 26 corresponds substantially to the thickness of the end ring 6 so that when the tabs are inserted in the slots, a relatively smooth surface on the exterior face of end ring 6 is provided.

After the blades 4 are placed in assembled relation with their opposite end tabs inserted in slots of their respectively opposite end rings, the tabs are held in secured relation to the end rings by one or more welding beads 30 applied to the outer surfaces of the rings and to the tab ends in an unbroken weld passing completely around the rings. This welding operation is performed on both the end ring 6 and the outer annular end ring portion 14 of the annular member 8, and on both of the equivalent members of the right wheel 16.

The pair of separate wheels 2 and 16 thus formed are mounted in end-to-end opposed relation with an inter vening central disc or backplate element 32 sandwiched between the left wheel annular member 8 and the right wheel annular member 22. A driving shaft hub 34 is concentrically mounted on the disc 32 with a series of bolts 36.

To fasten the two wheels together and to the disc 32, another series of bolts 38 Or other fastening means are provided. The bolts pass through registering holes provided in the inner annular portion 12 of the member 8 of the left wheel 2, the corresponding inner annular portion of the member 22 of the right wheel 16, and the outer annular portion of the backplate 32.

The central backplate 32 preferably has an outer diameter corresponding substantially to the outer diameter of the inner annular portions of the members 8 and 22 so that when the wheels 2 and 16 are assembled, an annular space 40 (FIGURE 1) is provided between the opposing outer annular portions of members 8 and 22. Thus the protruding ridges formed by the weld beads are held out of contact so that the face-to-face assembled members 8, 22 and 32 be held tightly one against another throughout their areas of surface contact.

The invention claimed is:

l. A centrifugal fan wheel comprising: a plurality of axially-extending fan blades arranged circumferentially around the axis of said wheel; a first end ring having a large central opening for the admission of air into said wheel, said first ring including means for securing one end of said blades thereto; a second end ring having a relatively smaller central opening, and including an outer annular portion having a plurality of slots for receiving therethrough the opposite ends of said blades with the end edges of said blades being substantially flush with the exterior face of said second end ring to provide a relatively flat surface to which a bead weld is applied for securing said opposite ends of said blades thereto, said second end ring including an inner annular portion divided into a plurality of segments defined between adjacent notch means extending outwardly from the inner peripheral edge of said second ring; a backplate member having a concentrically mounted hub and having an outer annular portion lapping, in face-to-face relation, said inner annular portion of said second end ring; and means for securing said inner annular portion of said second end ring to said backplate member.

2. In a double inlet centrifugal fan wheel formed of a pair of fan wheels secured together in mirror relation with an intermediate annular plate having a concentric hub: each of said wheels comprising a first end ring having a large central opening for the admission of air into said wheel, said first ring including means for securing one end of said blades thereto; a second end ring having a relatively smaller central opening, and including an outer annular portion having a plurality of slots for receiving therethrough the opposite ends of said blades with the end edges of said blades being substantially flush with the exterior face of said second end ring to provide a relatively fiat surface to which a bead weld is Cir applied for securing said opposite ends of said blades thereto, said second end ring including an inner annular portion divided into a plurality of segments defined between adjaeent notch means extending outwardly from the inner peripheral edge of said second ring; said intermediate annular plate is concentrically disposed between the opposing second end rings of said pair of wheels and has an outer annular portion lapping, in face-to-face relation, said inner annular portions of said second end rings; and fastening means for securing the inner annular portions of said second end rings to said outer annular portion of said intermediate annular plate.

3. In a fan wheel as specified in claim 2; said fastening means includes means disposed to extend through the central area of each of said segments.

4. A centrifugal fan Wheel of the welded character described comprising: a plurality of axially-extending, separate fan blades arranged circumferentially around a central axis with each blade having axially projecting opposite end tabs; a first end ring having a plurality of slots therein to receive said tabs on one end of said blades; a one piece second end ring including an outer annular portion having a plurality of slots therein to receive the tabs of the opposite ends of said blades, and an inner annular portion divided into a plurality of circumferentially-arranged segments formed by a corresponding number of circumferentially spaced notch means extending outwardly from the inner periphery of said inner annular portion; a backplate having a hub secured adjacent its inner periphery for securement to a driving shaft, and having its outer annular portion lapping, in face-to-face relation, the inner annular portion of said second end ring; and means for securing said individual segments to said outer annular portion of said backplate.

5. The fan wheel of claim 4 wherein: said end tabs project axially a distance equal to the thickness of said second end ring so that the end edges of said tabs are flush with the exterior face to provide a relatively fiat surface to which a bead weld is applied for securing said tabs to said second ring.

6. The fan wheel of claim 4 wherein: said notch means comprise radially-extending slots.

7. In a centrifugal fan wheel: a plurality of fan blades arranged circumferentially around the central axis of said fan wheel; a first end ring including a plurality of slots arranged circumferentially to receive the first ends of said blades for securement thereto in welded relation; an annular one piece member including an outer annular portion forming a second end ring provided with circumferentially arranged slots to receive the second ends of said blades for securement thereto in welded relation by applying a bead weld to the exterior surface of said second end ring, said one piece member including an inner annular portion having an inner diameter of substantially reduced dimension relative to the inner diameter of said first end ring and including a plurality of circumferentially-arranged notch means extending outwardly to divide said inner portion into a plurality of circumferentially-arranged separate segments; a backplate having a hub secured adjacent its inner periphery and having its outer annular margin lapping, in face-to-face relation, at least said inner annular portion of said one piece member; and means for securing said separate segments to said outer annular margin of said backplate.

References Cited in the file of this patent UNITED STATES PATENTS 905,460 Rice Dee 1, 1908 1,314,806 Hirt Set 1919 1,877,347 McMurdie Sept'fl3, 1932 1,985,705 Whiton Dec. 25, 1934 2,231,062 Evans Feb. 11, 1941 2,549,208 Rice Apr. 17, 1951 2,637,489 Place May 5, 1953 

